Corticocortical interactions in the primate visual system will be investigated to learn about the nature of the communication between cortical areas and how cortical regions interact in the analysis of the visual world. Paired electrophysiological recordings will be made between striate and extrastriate areas V1/V4, V1/IT and V4/IT in the awake-behaving monkey. Similar experiments will be performed in anesthetized monkeys. Visual stimuli will consist of both broadband and bandlimited noise as well as stimuli that allow for a separation of cortical feature extraction mechanisms from those of simple spatial filtering. Spike trains and local field potentials recorded in two visual areas will be analyzed for crosscorrelation structure in the presence and absence of visual stimuli and in the presence and absence of visually guided behavior. Corticocortical interactions will be studied in three different behavioral contexts. 1) focused spatial attention; 2) selective feature attention; 3) perception of simultaneous contrast. Current models of cortical organization suggest that these behaviors should influence the interactions between disparate cortical areas. The timing and distribution of activity in the cortical laminae of V1 and V4 will be examined with multicontact electrodes in the anesthetized monkey. This study will resolve the role of descending projections from extrastriate cortex in the processing of visual form in area V1. The regional and laminar pattern of neurofibrillary tangles has led to the conclusion that the dementia associated with Alzheimer's disease is a consequence of a loss of corticocortical projections. The development of more accurate diagnostic techniques may well depend on a better understanding of the nature of corticocortical interactions in the primate brain.